The present invention concerns a check valve for a filler pipe for the filling of a motor-vehicle fuel tank, having a housing fixed in the interior of the pipe and a movably mounted flap closure which is opened by the inflowing fuel and closes again automatically.
Various types of check valves can be fitted in filler pipes for the filling of a motor-vehicle fuel tank. A check valve is intended to prevent the fuel from rising back up into the filler pipe and escaping from the filling opening, as a result of the positive pressure occurring in the tank during filling, when the filling nozzle is switched off. The check valves do not have to provide a completely tight seal, but must oppose the return flow with adequate resistance, with the result that there is no undesired and troublesome escape of fuel from the filler pipe after filling.
Most of the check valves known for this purpose have spherical or conical valve bodies which, under the force of a weak spring, are directed against the filling flow and are opened by the inflowing fuel. The valves automatically close the opening when the inflowing fuel breaks off. There are configurations which are provided with elastomeric seals and also configurations which provide a seal only by resting on the valve seat. All of these known valves have the disadvantage that the fuel flow undergoes a sharp diversion. In the case of many configurations, it is only possible for the valves to be fitted at the end of the filler pipe or in a corresponding widening of the pipe, since the deflected fuel flow takes up space laterally. The fuel is subjected to great turbulence by the deflection, which leads to outgassing and hinders filling of the tank. The increased amount of gas must also be passed either into the ambient air or into active carbon filters, as are required for example in the USA, which entails further disadvantages.
Check valves of the type mentioned at the beginning which have a valve flap swivel-mounted laterally on the housing and held in the closed position either by its own weight or else under the force of a spring are also known. It is also the case with these valves that the opening and closing is brought about by the flow of fuel, as described above. In the case of these valves, the valve flaps have a much smaller diameter than corresponds to the inside diameter of the pipe, in order to be able to swing open. The mounting of the valve flap and the internal valve seating considerably reduce the cross-sectional area through which flow can pass, however, and the opened flap also causes great turbulence, which has the consequence of the outgassing described above.
It is a principal object of the present invention to design a check valve of the type described above wherein significantly less turbulence and disturbance of the flow of the fuel occurs during filling than is the case with known valve configurations, and consequently no or only insignificant outgassing takes place.